ApoA-I mimetic does not improve left ventricular diastolic dysfunction in rabbits without aortic valve stenosis.

BACKGROUND: We previously demonstrated that high-density lipoprotein (HDL) infusions may improve left ventricular diastolic dysfunction (LVDD) in an aortic valve stenosis (AVS) model. Whether the benefit was direct or mediated by the observed reduction in AVS severity is not clear. Here, we aimed to test the direct effect of an ApoA-I mimetic on LVDD in the absence of AVS. METHODS: Rabbits were exposed to three different protocols to develop LVDD. First, rabbits were exposed to 0.5% cholesterol-rich diet for an average of 17 weeks. Second, rabbits were subjected to surgical ascending aortic constriction (AAC), to mimic the effect of fixed reduced aortic valve area, and studied after 10 weeks. The third model combined both cholesterol-enriched diet (for 12 weeks) and surgical AAC. The control group consisted of age-matched rabbits under normal diet. After development of LVDD, rabbits were randomized to receive infusions of saline or apoA-I mimetic (25 mg/kg) 3 times per week for 4 weeks. Detailed cardiac structure and function measurements were assessed at baseline and weekly during treatment period. Histological and molecular analyses were performed on LV samples. RESULTS: In the three models, echocardiographic results showed development of LVDD over time, with preserved LV systolic and aortic valve functions versus controls. ApoA-I mimetic infusions did not significantly improve echocardiographic parameters nor molecular markers of cardiac inflammation, oxidative stress and fibrosis. CONCLUSION: ApoA-I mimetic therapy did not directly improve LVDD. These results indicate that previously observed changes of LVDD were caused by AVS improvement induced by this treatment.

Cardiac inflammation and diastolic dysfunction in hypercholesterolemic rabbits.

BACKGROUND: Left ventricular diastolic dysfunction (LVDD) is present in more than 50% of patients suffering from heart failure. LVDD animal models are limited and its underlying mechanisms remain largely unknown. Aortic valve stenosis (AVS) may cause LVDD, and we recently reported LVDD in an AVS rabbit model. Here we aimed to develop a rabbit model of LVDD without AVS. METHODS: Rabbits were fed with a 0.5% cholesterol-enriched diet (n = 9) or normal diet (n = 8) until they developed LVDD defined by a value of the echocardiographic parameter E/Em ratio higher than the mean at baseline + 2SD. Rabbits were then fed a 0.2% cholesterol-enriched diet for 4 weeks (average total diet duration: 20 weeks). Detailed cardiac structure and function measurements were assessed by echocardiography at baseline, weeks 8, 12 and 14 to 20, when applicable. Histological analyses and RT-qPCR were performed on LV samples. RESULTS: The hypercholesterolemic diet induced LVDD without systolic dysfunction or AVS, as shown by multiple echocardiographic parameters, including early filling mitral peak velocity and deceleration rate, Em/Am ratio and E/Em ratio (all p<0.05), and by increased cardiac mRNA expression of brain natriuretic peptide (Bnp). Cardiac expression of mRNA for Nox2, Vcam1, Mmp12, Mmp12/Timp1, Il1b and Col1/Col3 ratios was also higher in these rabbits (p<0.05). In contrast, cardiac Sod2 mRNA expression was reduced in hypercholesterolemic rabbits compared to controls. CONCLUSION: Rabbits fed with a cholesterol-enriched diet develop LVDD with preserved systolic function and evidence of cardiac inflammation and oxidative stress. This rabbit model may be used in future studies to test treatment strategies against LVDD.

In Vivo Near-Infrared Fluorescence Imaging of Atherosclerosis Using Local Delivery of Novel Targeted Molecular Probes.

This study aimed to evaluate the feasibility and accuracy of a technique for atherosclerosis imaging using local delivery of relatively small quantities (0.04-0.4 mg/kg) of labeled-specific imaging tracers targeting ICAM-1 and unpolymerized type I collagen or negative controls in 13 rabbits with atheroma induced by balloon injury in the abdominal aorta and a 12-week high-cholesterol diet. Immediately after local infusion, in vivo intravascular ultrasonography (IVUS)-NIRF imaging was performed at different time-points over a 40-minute period. The in vivo peak NIRF signal was significantly higher in the molecular tracer-injected rabbits than in the control-injected animals (P < 0.05). Ex vivo peak NIRF signal was significantly higher in the ICAM-1 probe-injected rabbits than in controls (P = 0.04), but not in the collagen probe-injected group (P = 0.29). NIRF signal discrimination following dual-probe delivery was also shown to be feasible in a single animal and thus offers the possibility of combining several distinct biological imaging agents in future studies. This innovative imaging strategy using in vivo local delivery of low concentrations of labeled molecular tracers followed by IVUS-NIRF catheter-based imaging holds potential for detection of vulnerable human coronary artery plaques.

Impact of summer season on pre-hospital time delays in women and men undergoing primary percutaneous coronary intervention.

BACKGROUND: Pre-hospital delays have been associated with poor outcomes in patients with acute ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). It is currently unknown how environmental variables affect treatment delays in these patients. METHODS AND RESULTS: The association between environmental variables, time to treatment including transportation times and adverse in-hospital events was assessed in 1828 consecutive patients with STEMI undergoing primary PCI between 2010 and 2014 in the Montreal metropolitan area. Median[Q1;Q3] total ischemia time was significantly longer during summer season (April-September) as compared to winter season (October-March, 201[140;305] min vs 187[126;266] min, p = 0.022). This difference between seasons was due to a significant increase in median decision time to seek treatment for symptoms during summer (90[46;185] min vs 78[40;156], p = 0.004). The former peaked during July and August and was most pronounced in men. Hence, outside temperature and summer season were identified as strong predictors of prolonged decision time in patients with STEMI (p < 0.001 and p = 0.002, respectively). Transportation times slightly increased during winter season and snow fall, this difference, however, was not significant (p = 0.46). A significant increase in in-hospital adverse outcomes following primary PCI was observed during summer season as compared to winter season (7.2% vs 4.8%, p = 0.032). Accordingly, multivariate logistic regression models adjusted for baseline variables identified summer season as a strong predictor of periprocedural adverse events (OR 1.83, 95% CI 1.2-3.11, p = 0.037). CONCLUSION: Contrary to our initial hypothesis, pre-hospital delays in patients with STEMI are considerably longer and associated with adverse in-hospital outcomes during summer season. Considering the consequences of global warming, it is imperative that educational efforts targeting patients' perception are implemented to counter treatment delays.

Weather and risk of ST-elevation myocardial infarction revisited: Impact on young women.

BACKGROUND: During the last decade, the incidence and mortality rates of ST-elevation myocardial infarction (STEMI) has been steadily increasing in young women but not in men. Environmental variables that contribute to cardiovascular events in women remain ill-defined. METHODS AND RESULTS: A total of 2199 consecutive patients presenting with acute ST-elevation myocardial infarction (STEMI, 25.8% women, mean age 62.6±12.4 years) were admitted at the Montreal Heart Institute between June 2010 and December 2014. Snow fall exceeding 2cm/day was identified as a positive predictor for STEMI admission rates in the overall population (RR 1.28, 95% CI 1.07-1.48, p = 0.005), with a significant effect being seen in men (RR 1.30, 95% CI 1.06-1.53, p = 0.01) but not in women (p = NS). An age-specific analysis revealed a significant increase in hospital admission rates for STEMI in younger women ≤55 years, (n = 104) during days with higher outside temperature (p = 0.004 vs men ≤55 years) and longer daylight hours (p = 0.0009 vs men ≤55 years). Accordingly, summer season, increased outside temperature and sunshine hours were identified as strong positive predictors for STEMI occurrence in women ≤55 years (RR 1.66, 95% CI 1.1-2.5, p = 0.012, RR 1.70, 95% CI 1.2-2.5, p = 0.007, and RR 1.67, 95% CI 1.2-2.5, p = 0.011, respectively), while an opposite trend was observed in men ≤55 years (RR for outside temperature 0.8, 95% CI 0.73-0.95, p = 0.01). CONCLUSION: The impact of environmental variables on STEMI is age- and sex-dependent. Higher temperature may play an important role in triggering such acute events in young women.

Hockey Games and the Incidence of ST-Elevation Myocardial Infarction.

BACKGROUND: The association between diagnosed acute ST-elevation myocardial infarction (STEMI) and hockey games in the Canadian population is unknown. METHODS: We retrospectively analyzed the association between hockey games of the National Hockey League Montreal Canadiens and daily hospital admissions for acute STEMI at the Montreal Heart Institute, Canada. RESULTS: Between June 2010 and December 2014, a total of 2199 patients (25.9% women; mean age, 62.6 ± 12.4 years) were admitted for acute STEMI. An increase in STEMI admissions was observed the day after a hockey game of the Montreal Canadiens in the overall population (from 1.3 ± 1.2 to 1.5 ± 1.3), however, this difference was not significant (P = 0.1). The number of STEMI admissions increased significantly from 0.9 ± 1.0 to 1.2 ± 1.0 per day in men (P = 0.04), but not in women (P = 0.7). The association between ice hockey matches and STEMI admission rates was strongest after a victory of the Montreal Canadiens. Accordingly, an increased risk for the occurrence of STEMI was observed in the overall population (hazard ratio [HR], 1.15; 95% confidence interval [CI], 1.0-1.3; P = 0.037) when the Montreal Canadiens won a match. This association was present in men (HR, 1.2; 95% CI, 1.03-1.4; P = 0.02) but not in women (P = 0.87), with a most pronounced effect seen in younger men (younger than 55 years; HR, 1.4; 95% CI, 1.1-1.8; P = 0.009). CONCLUSIONS: Although a weak association between hockey games and hospital admissions for STEMI was found in our overall population, the event of a hockey game significantly increased the risk for STEMI in younger men. Preventive measures targeting behavioural changes could positively affect this risk.

ADCY9 (Adenylate Cyclase Type 9) Inactivation Protects From Atherosclerosis Only in the Absence of CETP (Cholesteryl Ester Transfer Protein).

BACKGROUND: Pharmacogenomic studies have shown that ADCY9 genotype determines the effects of the CETP (cholesteryl ester transfer protein) inhibitor dalcetrapib on cardiovascular events and atherosclerosis imaging. The underlying mechanisms responsible for the interactions between ADCY9 and CETP activity have not yet been determined. METHODS: Adcy9-inactivated ( Adcy9Gt/Gt) and wild-type (WT) mice, that were or not transgenic for the CETP gene (CETPtg Adcy9Gt/Gt and CETPtg Adcy9WT), were submitted to an atherogenic protocol (injection of an AAV8 [adeno-associated virus serotype 8] expressing a PCSK9 [proprotein convertase subtilisin/kexin type 9] gain-of-function variant and 0.75% cholesterol diet for 16 weeks). Atherosclerosis, vasorelaxation, telemetry, and adipose tissue magnetic resonance imaging were evaluated. RESULTS: Adcy9Gt/Gt mice had a 65% reduction in aortic atherosclerosis compared to WT ( P<0.01). CD68 (cluster of differentiation 68)-positive macrophage accumulation and proliferation in plaques were reduced in Adcy9Gt/Gt mice compared to WT animals ( P<0.05 for both). Femoral artery endothelial-dependent vasorelaxation was improved in Adcy9Gt/Gt mice (versus WT, P<0.01). Selective pharmacological blockade showed that the nitric oxide, cyclooxygenase, and endothelial-dependent hyperpolarization pathways were all responsible for the improvement of vasodilatation in Adcy9Gt/Gt ( P<0.01 for all). Aortic endothelium from Adcy9Gt/Gt mice allowed significantly less adhesion of splenocytes compared to WT ( P<0.05). Adcy9Gt/Gt mice gained more weight than WT with the atherogenic diet; this was associated with an increase in whole body adipose tissue volume ( P<0.01 for both). Feed efficiency was increased in Adcy9Gt/Gt compared to WT mice ( P<0.01), which was accompanied by prolonged cardiac RR interval ( P<0.05) and improved nocturnal heart rate variability ( P=0.0572). Adcy9 inactivation-induced effects on atherosclerosis, endothelial function, weight gain, adipose tissue volume, and feed efficiency were lost in CETPtg Adcy9Gt/Gt mice ( P>0.05 versus CETPtg Adcy9WT). CONCLUSIONS: Adcy9 inactivation protects against atherosclerosis, but only in the absence of CETP activity. This atheroprotection may be explained by decreased macrophage accumulation and proliferation in the arterial wall, and improved endothelial function and autonomic tone.

Development of a new bioactivatable fluorescent probe for quantification of apolipoprotein A-I proteolytic degradation in vitro and in vivo.

BACKGROUND AND AIMS: The potential benefits of high-density lipoproteins (HDL) against atherosclerosis are attributed to its major protein component, apolipoprotein A-I (apoA-I). Most of the apoA-I in the vascular wall appears to be in its lipid-poor form. The latter, however, is subjected to degradation by proteases localized in atherosclerotic plaques, which, in turn, has been shown to negatively impact its atheroprotective functions. Here, we report the development and in vivo use of a bioactivatable near-infrared full-length apoA-I-Cy5.5 fluorescent probe for the assessment of apoA-I-degrading proteolytic activities. METHODS: Fluorescence quenching was obtained by saturation of Cy5.5 fluorophore molecules on apoA-I protein. ApoA-I cleavage led to near-infrared fluorescence enhancement. In vitro proteolysis of the apoA-I probe by a variety of proteases including serine, cysteine, and metalloproteases resulted in an up to 11-fold increase in fluorescence (n = 5, p ≤ 0.05). RESULTS: We detected activation of the probe in atherosclerotic mice aorta sections using in situ zymography and showed that broad-spectrum protease inhibitors protected the probe from degradation, resulting in decreased fluorescence (-54%, n = 6 per group, p ≤ 0.0001). In vivo, the injected probe showed stronger fluorescence emission in the aorta of human apoB transgenic Ldlr-/- atherosclerotic mice (ATX) as compared to wild-type mice. In vivo observations were confirmed by ex vivo aorta imaging quantification where a 10-fold increase in fluorescent signal in ATX mice (p ≤ 0.05 vs. control mice) was observed. CONCLUSIONS: The use of this probe in different applications may help to assess new molecular mechanisms of atherosclerosis and may improve current HDL-based therapies by enhancing apoA-I functionality.

Fabricating Water Dispersible Superparamagnetic Iron Oxide Nanoparticles for Biomedical Applications through Ligand Exchange and Direct Conjugation.

Stable superparamagnetic iron oxide nanoparticles (SPIONs), which can be easily dispersed in an aqueous medium and exhibit high magnetic relaxivities, are ideal candidates for biomedical applications including contrast agents for magnetic resonance imaging. We describe a versatile methodology to render water dispersibility to SPIONs using tetraethylene glycol (TEG)-based phosphonate ligands, which are easily introduced onto SPIONs by either a ligand exchange process of surface-anchored oleic-acid (OA) molecules or via direct conjugation. Both protocols confer good colloidal stability to SPIONs at different NaCl concentrations. A detailed characterization of functionalized SPIONs suggests that the ligand exchange method leads to nanoparticles with better magnetic properties but higher toxicity and cell death, than the direct conjugation methodology.

Hybrid FMT-MRI applied to in vivo atherosclerosis imaging.

Combining Fluorescent Molecular Tomography (FMT) with anatomical imaging, e.g. MRI facilitates interpreting functional information. Furthermore, using a heterogeneous model for light propagation has been shown in simulations to be superior to homogeneous modeling to quantify fluorescence. Here, we present a combined FMT-MRI system and apply it to heart and aorta molecular imaging, a challenging area due to strong tissue heterogeneity and the presence of air-voids due to lungs. First investigating performance in a phantom and mouse corpse, the MRI-enabled heterogeneous models resulted in an improved quantification of fluorescence reconstructions. The system was then used in mice for in vivo atherosclerosis molecular imaging. Results show that, when using the heterogeneous model, reconstructions were in agreement with the ex vivo measurements. Therefore, the proposed system might serve as a powerful imaging tool for atherosclerosis in mice.